Rockwell Automation 8520-GUM 9/Series CNC Grinder Operation and Programming Manual Documentation Set - Manual (Page 427)

Axis Motion
Chapter 12
12-55
For outside arc paths, the speed of the wheel surface relative to the part
surface can be determined using the following formula:
R
p
Wheel surface speed = F x ----
R
c
Where : Is :
F programmed feedrate
R
c
radius of the arc measured to the center of the wheel radius
R
p
programmed radius of the arc
Figure 12.27
Arc Feedrates during Dresser/Wheel Radius Compensation
programmed wheel path
wheel radius center path
Grinding
outside arc
R
c
R
p
R
p
R
c
Grinding
inside
arc
R
c
> R
p
F as programmed
R
c
< R
p
F is reduced
Grinding
wheel
Grinding
wheel
12038-I
For inside arc paths, the control automatically maintains the programmed
feedrate at the wheel surface. The actual wheel radius center feedrate is
reduced as needed through the arc path and then return to the programmed
feedrate after the arc is completed.
During inside arc paths, the control decreases the wheel radius center
feedrate by the ratio of R
c
/R
p
. If the R
c
value is very small compared to
R
p
, as in the case of a small arc being cut with a wheel with a large radius,
the value of R
c
/R
p
is nearly zero, and the wheel radius center feedrate
becomes excessively small.
To avoid this problem, your system installer must set a minimum feed
reduction percentage (MFR) in AMP. This sets a minimum feedrate to be
used whenever the value of R
c
/R
p
is very small. If R
c
/R
p
< MFR, the
control reduces the wheel radius center feedrate no more than the MFR
percentage.